Plasma processing system and plasma treatment process

Abstract

A plasma treatment system for treating multiple substrates with a plasma. The treatment chamber of the plasma treatment system includes at least one pair of electrodes, typically vertically oriented, between which a substrate is positioned for plasma treatment. Each electrode includes a perforated panel that permits horizontal process gas and plasma flow, which improves plasma uniformity. A process recipe is defined that is effective for removing thin polymer areas, such as flash or chad, attached to and projecting from a polymer substrate.

1 . An apparatus for treating substrates with a plasma generated from a process gas, comprising: 
 a treatment chamber including a processing space, a vacuum port for evacuating said processing space, and a gas port for introducing a process gas into said processing space;    a plasma excitation source capable of generating a plasma from the process gas in said processing space; and    a plurality of electrodes electrically coupled with said plasma excitation source, said electrodes arranged to define a corresponding plurality of processing regions therebetween in the processing space for treating the substrates with the plasma, and each of said electrodes including at least one perforated panel that operates to transfer the process gas and the plasma through each of said electrodes.    
   
   
       2 . The apparatus of  claim 1  wherein said perforated panel defines a surface area having a plurality of apertures with an open area of less than 20% of said surface area.  
   
   
       3 . The apparatus of  claim 1  wherein at least one of said electrodes includes a plurality of perforated panels each of which defines a surface area having a plurality of apertures and an open area of less than 20% of said surface area.  
   
   
       4 . The apparatus of  claim 3  wherein at least two of said perforated panels have a different open area.  
   
   
       5 . The apparatus of  claim 1  wherein each of said electrodes includes a frame carrying said perforated panel and an internal passageway in said frame adapted to receive a flow of a coolant liquid.  
   
   
       6 . The apparatus of  claim 1  further comprising: 
 a plurality of substrate holders positioned inside said treatment chamber, each of said substrate holders positioned in one of said processing regions, and each of said substrate holders supporting at least one of the substrates.    
   
   
       7 . The apparatus of  claim 6  wherein each of said substrate holders includes first and second frames configured to apply a clamping force on an outer perimeter of the substrate, said first and second frames defining a window between said adjacent pair of said electrodes through said substrate holder for plasma exposure of the substrate.  
   
   
       8 . The apparatus of  claim 6  wherein each of said substrate holders includes a first plurality of alignment posts projecting toward one of said adjacent pair of said electrodes and a second plurality of alignment posts projecting toward the other of said adjacent pair of electrodes, said alignment posts dimensioned to position said substrate in a plane substantially parallel to a plane defined by each of the adjacent pair of electrodes.  
   
   
       9 . The apparatus of  claim 6  wherein said substrate holders and the substrates are transferable from a plurality of loading positions outside said treatment chamber to said processing regions inside said treatment chamber.  
   
   
       10 . The apparatus of  claim 1  wherein each of said electrodes comprises an electrically-conductive core and a non-metal layer coating said core.  
   
   
       11 . The apparatus of  claim 1  wherein each of said electrodes includes a frame surrounding said perforated panel, said frame and said perforated panel having a uniform thickness across an area of the electrode.  
   
   
       12 . The apparatus of  claim 1  wherein each of said electrodes includes a plurality of perforated panels each configured to transfer the process gas and the plasma through each of said electrodes.  
   
   
       13 . The apparatus of  claim 1  wherein said electrodes are arranged in substantially parallel planes having a flanking relationship to define said processing regions.  
   
   
       14 . A method of plasma treating a substrate, comprising: 
 supporting the substrate in a processing region defined inside a treatment chamber between a pair of electrodes;    introducing a process gas into the treatment chamber;    energizing the pair of electrodes to generate a plasma within the treatment chamber from the process gas; and    directing a flow of the process gas and the plasma through a porous portion of each of the electrodes from a location outside the processing region to a pair of locations inside the processing region each defined between one of the electrodes and the substrate.    
   
   
       15 . The method of  claim 14  further comprising: 
 supporting the substrate between the pair of electrodes with a substrate holder; and    cooling the substrate holder and the substrate while exposed to the plasma.    
   
   
       16 . The method of  claim 14  wherein the porous portion of each of the electrodes is a perforated panel between the location outside the processing region and one of the locations inside the processing region, and directing the flow of the process gas and the plasma through the electrodes further comprises: 
 transmitting the flow of the process gas and the plasma through the perforated panel in each of the electrodes.    
   
   
       17 . A method for removing thin attached polymer areas projecting from a polymer substrate, comprising: 
 supplying a process gas to a treatment chamber holding the polymer substrate, the process gas including a gas mixture containing oxygen and nitrogen trifluoride, and nitrogen trifluoride comprising less than or equal to about 10 percent by volume of the gas mixture;    generating a plasma from the process gas; and    exposing the polymer substrate to the plasma for a time effective to remove the thin attached polymer areas.    
   
   
       18 . The method of  claim 17  wherein generating the plasma further comprises: 
 transferring power to the process gas in a range of about 4000 watts to about 8000 watts at 40 kHz.    
   
   
       19 . The method of  claim 17  further comprising: 
 heating the polymer substrate to a process temperature above ambient temperature.    
   
   
       20 . The method of  claim 19  wherein heating the polymer substrate further comprises: 
 heating the polymer substrate to a process temperature in the range of about 30° C. to about 90° C.    
   
   
       21 . The method of  claim 19  wherein heating the polymer substrate further comprises: 
 supporting the polymer substrate in thermal contact with a substrate holder; and    cooling the substrate holder with a coolant flow to remove heat transferred from the plasma to the polymer substrate.    
   
   
       22 . The method of  claim 17  wherein generating the plasma further comprises: 
 positioning the polymer substrate in a processing region defined between a pair of electrodes; and    transferring the plasma and the process gas through a perforated panel in each of the pair of electrodes to the processing region.    
   
   
       23 . The method of  claim 22  further comprising: 
 cooling the electrodes with a coolant flow to reduce heat transferred from the electrodes to the polymer substrate.    
   
   
       24 . The method of  claim 17  wherein the gas mixture comprises about 5 percent by volume to about 10 percent by volume of nitrogen trifluoride and the balance oxygen.  
   
   
       25 . The method of  claim 17  wherein the thin attached polymer areas leave a residue on the polymer substrate after being exposing to the plasma, and further comprising: 
 changing the gas mixture such that nitrogen trifluoride comprises greater than or equal to about 90 percent by volume of the process gas; and    exposing the polymer substrate to the plasma for a time effective to remove the residue.    
   
   
       26 . The method of  claim 25  wherein the gas mixture comprises about 90 percent by volume to about 95 percent by volume of nitrogen trifluoride and the balance oxygen.  
   
   
       27 . The method of  claim 25  wherein the gas mixture is changed without extinguishing the plasma.